Satgen352     Spacewatch - Asteroid Probes  by GM4IHJ          22 Dec 95

Recent events, such as the collision of Comet Shoemaker-Levy with Jupiter
, and the scare caused by incorrect reports of a possible collision
between Earth and Comet Swift-Tuttle, have heightened interest in
Spacewatch ( Satgen223 ) the dedicated search for potentially dangerous
Comets and Earth orbit crossing Asteroids. It is no surprise therefore
that a new type of Asteroid survey mission has recently been proposed.

What is interesting about this proposal is that it comes from the US
Military, not from NASA. Previously NASA had been thought to be the
logical agency for this type of experiment, but it does seem sensible for
the military to take a hand, if you consider their responsibility for
protecting the USA.

The proposed mission will be a follow on to the recent Clementine 1. Which
used a small ( cheap by military/NASA standards ) satellite and ground
control system, to operate a Moon mapping mission . Unfortunately a
subsequent Asteroid rendezvous mission had to be aborted because of a
software glitch. But considering that the missions main purpose was
testing new systems with the lunar and asteroid experiments as extras, it
was a considerable success. 

This success will now be followed up by Clementine 2, which like its
predecessor will be a system test vehicle. This time asteroid rendezvous
will be the supplementary experiment, with the satellite firing small
kilogram telemetry broadcasting packages at the asteroids it meets, and
analysing their composition and structure, on a basis of impact products
and degree of damage/cratering of the target. If this mission succeeds ,
further missions targeted at specific earth orbit crossing/potentially
dangerous asteroids , are planned.

The recent dramatic collisions of relatively small Comet Shoemaker-Levy
fragments with Jupiter, surprised almost all observers with the severity
of the explosions generated. Fortunately the Earths gravity is far less
than Jupiters , so we pull in 100 times less fragments than Jupiter does,
but those that do come our way , will on the evidence of Shoemaker-Levy be
far more dangerous and destructive than had previously been anticipated.
So the fact that the US Air Force has decided to get involved in policing
the High Frontier, should surprise no one.

Meanwhile, speaking of Comets, or more correctly the extinct comet , now
an asteroidal cinder which was the progenitor of the Geminids meteor
stream. The most recent crossing of the old comets dust trail 13 to 15th
Dec 95 , produced some of the best meteor scatter this observer has seen
for years. Seated indoors on the evenings 13 and 14th of December with a
DX TV set tuned to Scandinavian commercial TV, this observer had excellent
locked video sometimes for 20 seconds at a time from more than 8 stations
across Sweden, Norway and Denmark, propagated to Scotland via the ionised
trails produced by the destruction of quite sizable meteors as they were
heated by collision with the upper atmosphere. A feat which has only been
bettered once before in a superb Quadrantids shower of a few years ago. I
wonder will the next Quadrantids due early am utc on 4th January 96 , be
as good.